INVITATION TO CYBERSECURITY 28 CPUs and RAM. Running too many VMs consumes a computer’s resources and makes it unusable. The idea of virtualizing hardware has been around for decades, but it became cost-effective for the average computer user in the 2010s. Since that time, the use of VMs has exploded because they provide many benefits. One of their benefits is that VMs can be saved and copied like any other computer file. This makes it possible to customize a VM and then distribute copies of it to others—it is like “cloning a laptop” and giving the copies to friends. This practice is prevalent in the world of cybersecurity. Experts configure VMs with open-source hacking tools, and then make them freely available for download. One of the most popular of these cyber VMs is Kali Linux (see Figure 2.9). Figure 2.9 A Kali Linux VM running as a browser-based application. Another benefit of VMs is that machine states can be saved efficiently. This functionality is called taking a snapshot. A snapshot is a capture of the complete state of a VM at a point in time. Users can take snapshots and revert back to them later. A practical application of this is taking a snapshot before making a series of changes to a VM. If the changes do not work out as expected, it is easy to revert back to the pre-changes snapshot. At that point, it is like the changes never happened, so there is no worry about lingering effects that may be difficult to undo. Reverting to a snapshot is like going back in time. VMs can also be used as sandboxes. A sandbox is a compartmented safe space for testing and exploring. Like in the example above, a cyber researcher may want to explore a computer virus but be worried that it may end up infecting his own computer. In that case, he can examine the virus within a guest VM (although some sophisticated types of malware have been known to “escape” from VMs and infect the host OS, so even this is not without risk!). If the guest VM ends up being compromised, no problem—it can be reverted to an earlier snapshot, or if needed, it can even be destroyed. VMs are “cheap”
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